Tektronix TDS1000- Bedienungsanleitung PDF herunterladen (Seite 138)

Math FFT

120

TDS1000/2000-Series Digital Oscilloscope User Manual

Selecting an FFT Window

Windows reduce spectral l eakage in the FFT spectrum. The FFT

assumes that the YT waveform repeats forever. With an integral

number of cycles (1, 2, 3, ...), the YT waveform starts and ends at the

same amplitude and there are no discontinuities in the signal shape.

A non-integral number of cycles in the YT waveform causes the

signal start and end points to be at di fferent a mplitudes. The

transitions between the start and end points cause discontinuities in

the signal that introduce hi gh-frequency transients.

Time-domain

(YT) waveform

Without windowing

FFT

Discontinuities

Center 2048

data points

1 2 ... 133 134 135 136 137 138 139 140 141 142 143 ... 205 206

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Tektronix TDS1000- Bedienungsanleitung Seite 138